Method 8 was developed specifically for measuring sulfur oxide emissions from sulfuric
acid manufacturing plants. These sources have relatively clean and dry emission streams
with few or no interferences. Method 8 works very well for these kinds of sources.

Because Method 8 is the only method that EPA has published for measuring sulfuric acid/sulfur
trioxide emission, it has been applied to many source categories other than the one for which it
was developed. It may not work very well for some source categories and may not be appropriate
for measuring sulfur oxide emissions from them. It should not be used to measure
sulfuric acid/sulfur trioxide from the following kinds of sources:

1. Those sources that have significant emissions of solid sulfates that are water
soluble. Solid sulfates are compounds like sodium sulfate.

2. Those sources that have significant emissions of sulfur dioxide and ammonia.

Method 8 uses a manual sampling train similar to the one described in EPA Method 5 to collect particulate matter
samples. The principle difference is that the filter in Method 8 is not between the probe
and first impinger but between the first and second impingers. In addition,
there is no requirement to heat the filter. The Method 8 sample train begins with a
glass probe to transfer the sample from the stack to the first impinger. The
first impinger contains an 80% solution of isopropyl alcohol in water. This
impinger is followed by a glass fiber filter. The filter is followed by two
impingers each containing a 3% solution of hydrogen peroxide in water, and
empty impinger, and an impinger containing silica gel. The impingers are followed
by a combination pump and meter box system to pull sample from the stack at a
controlled rate and measure the volume.

The stack is divided into a predetermined number of equal areas. The sample is
collected from the centroid of each of these areas for an equal length of time at a
sampling rate that is isokinetic with the stack flow rate at the point of sample
collection. As the sample passes through the sample train the sulfuric acid/sulfur
trioxide is collected in the first impinger and on the filter behind the first impinger.
The sulfur dioxide continues past the first impinger and filter and is collected in the
second and third impingers. Samples are typically collected for a total period
of an hour.

Method 8 physically separates the sulfuric acid/sulfur trioxide from the sulfur
dioxide in the sample train. At the conclusion of the sample collection, the
sulfuric acid/sulfur trioxide sample is contained in the isopropyl alcohol
solution recovered from the first impinger and the backup filter. The sulfur
dioxide sample is contained in the hydrogen peroxide solution recovered from the
impingers two and three. Once the sulfur oxides are collected, they are in the
chemically identical form of a sulfuric acid solution. The analysis for both
sample fractions is removed and placed in a flask. Isopropyl alcohol is added
to the sample to adjust the concentration of the alcohol to at least 80%. A few
drops of a solution of Thorin is added to the sample, and the sample is titrated
with a 0.01 N solution of barium perchlorate until the color of the sample changes
from straw yellow to salmon pink.

The analysis can be performed at the test site or the sample may be returned to the
laboratory for analysis. There is no requirement on how quickly the sample must
be analyzed because the samples are chemically stable for long periods of time.
However, good laboratory practice would require that the samples be analyzed as
soon after collection as practical.

Do you have questions about a Test Method, Performance Specification or Source Category? Find the EMC contact
for your question by clicking on the "EMC Contacts" link at the menu on the left of your screen, or
use the direct link here.